My impression had been very negative because I'd been playing around with Windows 8 on old, non-touch-screen hardware -- basically Windows 7 laptop and desktop computers that had been upgraded to beta versions of Windows 8 in various stages beginning in February.

Using Windows 8 on a non-touch PC is a major pain. The new tiles and menu/touch-points do not lend themselves to a trackpad or mouse. Why? Because you have to hunt from side to side, from corner to corner, and that is an exercise in frustration. Beta-user feedback seemed overwhelmingly negative, confirming my own experience.

But then on Oct. 25 and 26, something happened. For the first time, I got to use both desktop/tablet versions of Windows 8 on purpose-built touch-screen hardware. As it turns out, this made all the difference.

Practically, how does this work? The point here is that as a user, you will be spending most of your time in the major Office apps (Outlook, Word, Excel, PowerPoint), a browser and some other apps you may use such as Skype and Apple's (AAPL) iTunes. When you use most of these apps, you will not need a touch screen. You will use a trackpad or mouse just as would with Windows 7.

However, when you switch apps -- and, more importantly, when you start the computer -- you will find that you prefer to use the touch screen. It's just faster, easier and more logical that way. That's why a touch screen makes all the difference in terms of Windows 8 being an acceptable platform.

In other words, you will be spending 99% of your time in Windows 8 using a trackpad/mouse as usual. The problem is that if the other 1% is dysfunctional, it completely ruins the experience for the other 99%. As a result, you should at all cost avoid running Windows 8 on a non-touch-screen PC. Without a positive 1%, the other 99% will be miserable.

Still, using Windows 8 on a purpose-built touch screen is not necessarily enough to make the operating system a success. Even if that 1% touch-screen experience is as smooth as can be, it comes with a learning curve. The absence of a start button in particular means that you have to figure out basic menu navigation. Learning this may take some people five minutes or less, but for others it could require up to 25 minutes.